/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http;

import java.util.function.Supplier;

import org.reactivestreams.Publisher;

import reactor.core.publisher.Mono;

import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;

/**
 * A "reactive" HTTP output message that accepts output as a {@link Publisher}.
 *
 * <p>Typically implemented by an HTTP request on the client-side or an
 * HTTP response on the server-side.
 *
 * @author Arjen Poutsma
 * @author Sebastien Deleuze
 * @since 5.0
 */
public interface ReactiveHttpOutputMessage extends HttpMessage {

    /**
     * Return a {@link DataBufferFactory} that can be used to create the body.
     *
     * @return a buffer factory
     * @see #writeWith(Publisher)
     */
    DataBufferFactory bufferFactory();

    /**
     * Register an action to apply just before the HttpOutputMessage is committed.
     *
     * @param action the action to apply
     */
    void beforeCommit(Supplier<? extends Mono<Void>> action);

    /**
     * Whether the HttpOutputMessage is committed.
     */
    boolean isCommitted();

    /**
     * Use the given {@link Publisher} to write the body of the message to the
     * underlying HTTP layer.
     *
     * @param body the body content publisher
     * @return a {@link Mono} that indicates completion or error
     */

    Mono<Void> writeWith(Publisher<? extends DataBuffer> body);

    /**
     * Use the given {@link Publisher} of {@code Publishers} to write the body
     * of the HttpOutputMessage to the underlying HTTP layer, flushing after
     * each {@code Publisher<DataBuffer>}.
     *
     * @param body the body content publisher
     * @return a {@link Mono} that indicates completion or error
     */
    Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body);

    /**
     * Indicate that message handling is complete, allowing for any cleanup or
     * end-of-processing tasks to be performed such as applying header changes
     * made via {@link #getHeaders()} to the underlying HTTP message (if not
     * applied already).
     * <p>This method should be automatically invoked at the end of message
     * processing so typically applications should not have to invoke it.
     * If invoked multiple times it should have no side effects.
     *
     * @return a {@link Mono} that indicates completion or error
     */
    Mono<Void> setComplete();

}
